/Falcon-OS

Bare-metal terminal program (high school hobby project).

Primary LanguageAssembly

Screen Shot 2022-03-02 at 7 49 18 AM

Falcon-OS 🦅

My go at writing an operating system - written in x86 assembly and C/C++.

The term "operating system" is used very loosely. There is a terminal, and there exists two commands. That's it.

Commands

Canonical "Hello, World!" program

hello

Prints out the first 10 numbers of the fibonacci sequence in hexadecimal.

fib

Steps for Building

This project can only be built in a Linux environment - Windows and macOS users beware.

When building this project, I run Ubuntu 20.04.3 in VirtualBox. The OS is built as a binary that is then loaded via grub.

I am unsure if the project will work when running Ubuntu as a native host. My best guess is that this should work as well.

Start by cloning the repo and installing the necessary tools for building the OS.

sudo apt-get install make nasm

To build and install the OS binary, run make

make install

To run the OS, it will depend on the configuration of your Ubuntu install. We run the OS by selecting "Falcon OS" as a menu option in grub. On a default Ubuntu install, the grub menu is disabled.

Enabling the grub menu

The following instructions are in reference to this stack exchange discussion: https://askubuntu.com/questions/182248/why-is-grub-menu-not-shown-when-starting-my-computer

Open /etc/default/grub

sudo nano /etc/default/grub

Comment out the lines "GRUB_TIMEOUT_STYLE=hidden" and "GRUB_TIMEOUT=0". Also uncomment "GRUB_TERMINAL=console".

Write to the file with ctrl+o and close nano with ctrl+x.

Finally, we must insert a menu entry for our OS into grub.cfg. Run make install again.

make install

Simply reboot your computer (or the VirtualBox VM), then select "Falcon OS" from the menu.

Features

  • grub loads the kernel, which does the following before handing off control to the custom terminal program

    • Sets up a program stack
    • Sets up the global descriptor table
    • Sets up the interrupt descriptor table and enables interrupts

  • The terminal program uses the following kernel functionality

    • Text printing to the screen via VGA text mode
    • Interrupt driven keyboard support via PS/2 controller IO ports